Leaking bathroom exhaust fan

[Khayes]

I am considering purchasing a 4-year-old investment property. At a recent walk-thru we noticed the bathroom ceiling texture was crumbling away around the exhaust fan and it appeared to have a water stain. I checked in the attic and here's the deal. First the vent piping is silver flex hose and runs from the fan straight up through the roof - a nearly vertical distance of about 10 feet. At the bottom of the hose, just as it connects to the exhaust fan, there is a small kink and believe it or not, it is filled with water just like a P-Trap. When I flexed the pipe, water poured through the fan to the bathroom below.

My question - is the fan vented properly? I'm concerned with the long vertical length of piping that the fan cannot push the moist air up such a distance. Can that be causing the accumulation of water? Can I just replace it with a rigid exhaust pipe? This would eliminate the kink. Or could the water be coming in from possibly being improperly capped on the roof side?

Thanks.

 

[Bob NH]

The water could come from two sources:
1. Rain falls inside the pipe.
2. The temperature in the pipe is lower than the dew point in the air being exhausted from the bathroom.

In the case of the cold pipe, the water that would otherwise be condensed on the mirror is now being condensed on the inside of the pipe and collecting in the "trap".

If the pipe is routed to the soffit so it drains downward quickly after it enters the attic, and the "trap" is eliminated, it should solve the problem. The air that is exhausted after the shower is turned off will have some capacity for water vapor and will carry away anything that is condensed in the parts of the pipe near the fan.

It would help if exhaust pipe is insulated, especially the section near the fan.

 

[Sponsor]

 

[Jadnashua]

Rigid insulated ductwork that doesn't slow the air down and a proper exhaust vent on the roof with a damper that can prevent wind blown rain into it should go a long ways to solving this problem.